Definition
An ATC altitude restriction requiring the pilot to cross a specified fix at or above a stated altitude. The pilot may cross the fix at the assigned altitude or any higher altitude, but must not be lower than the stated altitude when crossing the fix.
Plain English
When you reach the named point on your route, you must be at the given altitude or higher — never below it.
Context Anchor
Used in air traffic control clearances and on published arrival or departure procedures when a pilot must meet a minimum altitude at a specific point.
Derivation
Altitude comes from the Latin altus, meaning high. In aviation, it means height measured from a known reference, and in this phrase it marks the lowest height allowed when crossing the named point.
Why Pilots Care
Ensures required obstacle clearance and traffic separation while giving pilots flexibility to stay higher for performance, weather, or comfort.
Intuition Check
At or above does not mean aim for exactly that altitude. It means do not cross the fix below the stated altitude; higher is acceptable only if the rest of the clearance or procedure allows it.
Example Sentence 1
ATC instructed the pilot to cross BRAVO at or above 8,000, so he leveled at 9,000 and crossed the fix without descending further.
Example Sentence 2
The STAR shows cross ABC at or above 4000 to keep terrain clearance while allowing a higher altitude if the aircraft is heavy.